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Updated: Aug 11, 2026
Qualitative and Quantitative Analysis of Siderophore Production from Pseudomonas aeruginosa
Published on: March 15, 2024
Binding properties of pyochelin and structurally related molecules to FptA of Pseudomonas aeruginosa
Gaëtan L A Mislin1, Françoise Hoegy, David Cobessi
1Métaux et Microorganismes: Chimie, Biologie et Applications, UMR 7175-LC1 Institut Gilbert-Laustriat, CNRS, Université Louis Pasteur (Strasbourg 1), ESBS, Bld Sébastien Brant, F-67413 Illkirch, Strasbourg, France.
Abstract:
Pyochelin (Pch) is a siderophore that is produced in iron-limited conditions, by both Pseudomonas aeruginosa and Burkholderia cepacia. This iron uptake pathway could therefore be a target for the development of new antibiotics. Pch is (4'R,2''R/S,4''R)-2'-(2-hydroxyphenyl)-3''-methyl-4',5',2'',3'',4'',5''-hexahydro-[4',2'']bithiazolyl-4''-carboxylic acid, and has three chiral centres located at positions C4', C2'' and C4''. In P.aeruginosa, this siderophore chelates iron in the extracellular medium and transports it into the cells via a specific outer membrane transporter FptA. Docking experiments using the X-ray structure of FptA-Pch-Fe showed that iron-loaded or unloaded Pch diastereoisomers could bind to FptA. This was confirmed by in vivo binding assays. These binding properties and the iron uptake ability were not affected by removal of the C4' chiral centre. After removal of both the C4' and C2'' chiral centres, the molecule still bound to FptA but was unable to transport iron. The overall binding mode of this iron-complexed analogue was inverted. These findings describe the first antagonist of the Pch/FptA iron uptake pathway. Pch also complexes with iron in conjunction with other bidentate ligands such as cepabactin (Cep) or ethylene glycol. Docking experiments showed that such complexes bind to FptA via the Pch molecule. The mixed Pch-Fe-Cep complex was also recognized by FptA, having an affinity intermediate between that for Pch(2)-Fe and Cep(3)-Fe. Finally, the iron uptake properties of the different Pch-related molecules suggested a mechanism for FptA-Pch-Fe complex formation similar to that of the FpvA/Pvd uptake system. All these findings improve our understanding of specificity of the interaction between FptA and its siderophore.
Insights
Pyochelin (Pch), a siderophore used by bacteria for iron uptake, can be targeted for new antibiotics. Researchers identified modified Pch molecules that bind to the FptA transporter but block iron transport, acting as antagonists.
Area of Science:
- Microbiology
- Biochemistry
- Drug Discovery
Background:
- Pyochelin (Pch) is a siderophore essential for iron acquisition by Pseudomonas aeruginosa and Burkholderia cepacia under iron-limited conditions.
- The Pch-iron uptake pathway, mediated by the outer membrane transporter FptA, represents a potential target for novel antibiotic development.
Purpose of the Study:
- To investigate the structure-activity relationship of Pyochelin (Pch) and its interaction with the FptA transporter.
- To identify potential antagonists of the Pch/FptA iron uptake pathway for antibiotic development.
Main Methods:
- Utilized X-ray crystallography and docking experiments to analyze the binding of Pch diastereoisomers and modified analogues to FptA.
- Performed in vivo binding assays to confirm interactions and assess iron uptake capabilities.
Main Results:
- Pch and its iron complexes bind to FptA, with binding affinity influenced by chiral centers.
- Removal of specific chiral centers (C4' and C2'') resulted in molecules that bind FptA but inhibit iron transport, acting as antagonists.
- Mixed siderophore complexes (Pch-Fe-Cep) also bind to FptA, with affinity modulated by the ligands involved.
Conclusions:
- The study identified the first antagonists of the Pch/FptA iron uptake pathway, offering a promising avenue for antibiotic discovery.
- Findings elucidate the specificity of FptA interactions with siderophores and their complexes, contributing to understanding bacterial iron acquisition mechanisms.
